mip_matteshadow (cameramap?) gives blurry transparency

#1

Wasn’t quite sure how to title this, but that’s basically what’s happening.

I’m using mip_matteshadow on a plane to catch a minor shadow, and the cameramap is mapped to an image that fills the environment, etc. However, the plane never goes fully transparent because it slightly blurs everything behind it. See the attached pic where the top shows an outline of where the plane is, the middle illustrates how blurred the background is right behind that area but nowhere else, and the third is how it should look (I had to turn off visibility on the plane just to get the third clear picture)!

The matteshadow does capture the shadow, and basically things are working as they should except for the blurring that’s happening and wrecking the results. I’ve tried going through every option and check box related to the plane, the matteshadow settings, the cameramap settings, lights, camera, render settings, and turned everything on and off one at a time to test render and see if I could determine what’s causing this. I am out of ideas, so I’d sure appreciate if anyone has seen this before and could clue me in.
Thanks…

#2

To follow-up quickly and possibly have resolved my own problem…I’ve realized that this seems to have to do with the image sequence I have mapped to the cameramap node. This is an animated sequence and the cameramap background environment goes also to the matteshadow background for the area covered by the small plane. (That said, this might just as well apply to a static image, since the only difference would be selecting “Use Image Sequence”.)

Under the mip_camerapmap node, where “Map” is listed showing the name of the image to use, click at the end of the filename to see the settings for the image itself (the full path to the directory where the image is located, etc.). At the top of the section “File Attributes” is a choice for ‘Filter Type’…and that seems to have been the problem. It was set by default to Quadratic (I’m presuming that’s the default)…but if I turn it “OFF” then the plane no longer appears as the blurry area. Any other filter type yields a blurry transparency.

So, anyone know why a ‘filter type’ would blur the transparency of a matteshadow material in use like this?

#3

Yes, filter type and filter strength can play a huge role in how a texture renders. Imagine your image in Photoshop, and you’re applying a simple gaussian blur filter - that’s similar to how texture filtering works at rendertime. Bump maps, displacement maps, and other value-based texture maps instead of color-based ones should almost always be left with the filtering off.

For photo-based textures however, various filters yield cleaner, faster results. MipMap with a strength of .2 for alpha-cutout leaves, for example, but only on the diffuse texture, not the cutout opacity texture or bump. Elliptical filtering for solid textures works great too.

I don’t use the matteshadow much so this result you saw was unexpected, but I’m glad you fixed it!